This invention relates to a method and apparatus for processing photographic material. In particular, the invention relates to a method of processing which uses a low volume of processing solution.
Conventional processing of photographic material requires the use of large tanks of processing solutions. Each tank contains a processing solution such as developer, bleach, fixing solution or washing solution. The material is transported through each tank in turn. There is a tendency for the solutions to carry over from one tank to another leading to pollution of the solutions. Conventional processing has several other drawbacks. The temperatures which can be utilized are limited and therefore the process is slow. The composition of the solutions must be stable over long time residence periods in the processing tanks. Replenishment of the solutions is difficult to control. The processing apparatus is also very large due to the number of processing tanks and the apparatus is limited to only one type of process.
To overcome the problems of conventional deep tank processing surface application of the processing chemicals was developed. In previous surface application methods a volume of solution is applied to the surface of the material being processed. However, previous surface application methods have several drawbacks. If the solution applied to the material is just left on the sensitized surface of the material in a static condition the processing will be very slow and inefficient because there is no agitation and by-products accumulate in the material and solution layers, slowing down the processing. This method is also prone to non-uniformity of processing.
It is also known to process the material within a rotary tube. The material to be processed is placed emulsion side facing inwards within the tube. Solution is added and the tube rotated. Large volumes of processing solution (70 ml/sq.ft and upwards) will process the material effectively so long as rotation is not so fast as to cause dispersion of the solution puddle. Rapid rotation of the device is however very desirable to quickly and evenly distribute a given small volume of solution over the whole surface of the material so that processing is uniform from one end to the other. If the rotation is too slow there will be seasoning of the small volume of solution by the front end of the material and processing will be different at the back end of the material. Small volumes of processing solution (50 ml/sq.ft or less) do not properly process film or paper because when the device is rotated, even at low speeds of rotation, the solution puddle is dispersed and spread over the whole surface of the material. Consequently there is no agitation. This leads to several processing defects. Processing is similar to that already described and can be streaky, non-uniform and slow because of local consumption and the production of by-products. There is no surface mixing and chemical economy is therefore low.
Co-pending application GB 0023091.2 discloses a processor having a cylindrical chamber which is rotated during processing. Film is loaded around the inner circumference of the chamber when the chamber is stationary. One method of loading film into the chamber of the processor is to provide an entry slot in the outer circumference and feed the film through the slot and round the inner circumference. The film is driven by a pair of rollers just outside the entry slot. This method has been described in the above mentioned co-pending application, in which edge guides are also provided to keep the film against the inner circumference and prevent it falling into the centre of the chamber. The edge guides overlap the film edges on both sides by about 2 mm thus providing film retention and also free access of processing solution to the image area and back of the film.
The method described in the above-mentioned application is very effective. However, it can only apply to a fixed film width such as 35 mm or 24 mm (APS). Both widths of film cannot be processed in the same chamber. It has been found that when one side of a 24 mm film is fed into one of the edge guides of a chamber designed for 35 mm film, the 24 mm film will sometimes fall out before loading is complete. The 24 mm film is then not properly loaded and cannot be processed. A chamber designed for film 24 mm wide clearly cannot accept film 35 mm wide. To overcome these difficulties a new apparatus and method of loading the film has been designed and this is the subject of the present application.
According to the present invention there is provided an apparatus for processing photographic material comprising a chamber adapted to hold the material therein, means for introducing solution into the chamber, means for removing the solution from the chamber, and a member located within the chamber and filling a central part thereof, a gap being defined between the inner wall of the chamber and the central member in which the material is located, thereby to retain the material around the inner circumference of the chamber.
The central member can be made of a material which does not damage the emulsion on the film. Preferably the inner circumferential wall of the chamber is made of the same material. The inner wall may also be provided with rollers to reduce the friction and damage. However this is not an essential feature of the invention.
Advantageously the apparatus may be provided with a double slot edge guide entry to further facilitate film of two widths being loaded into the same chamber. However this is not an essential feature of the invention.
The invention further provides a method of processing photographic material comprising the steps of loading the material into a processing chamber the central part of which is filled by a central member, the walls of the chamber and the central member defining a gap in which the material is located, introducing processing solution into the chamber, agitating the solution and removing the solution from the chamber.
Preferably the solution is agitated by means of a roller located within the gap defined by the wall of the chamber and the central member.
The invention further provides an apparatus for processing photographic material comprising a chamber adapted to hold the material therein, means for introducing solution into the chamber, means for removing the solution from the chamber, a member located within the chamber and filling a central part thereof, a gap being defined between the inner circumferential wall of the chamber and the central member, the central member having at least one nest defined therein.
The invention further provides a method of loading film into a processor wherein the material is introduced into the chamber with both the chamber and the central member being stationary, the fed material entering a nest defined in the central member and forming a roll therein, once the material is fully introduced into the chamber the chamber being rotated and the central member remaining stationary thus unrolling the material along the inner circumference of the chamber for processing.
Preferably concave rollers are used to prevent damage to the film and prevent sticking of the wetted emulsion.
The present invention allows various widths of film to be loaded into a single drum processing chamber. It is not necessary for the drum chamber to have edge guides. Any length of film, up to the circumference of the chamber, can be loaded into the chamber. The film may remain attached to the film cassette during processing.
Having a member filling a central part of the chamber cuts down on heat loss and evaporation of the processing solution. This leads to energy saving and more economic running of the processor.